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Commit 1d486bfb authored by Veaceslav Falico's avatar Veaceslav Falico Committed by David S. Miller
Browse files

net: add NETDEV_PRECHANGEMTU to notify before mtu change happens 



Currently, if a device changes its mtu, first the change happens (invloving
all the side effects), and after that the NETDEV_CHANGEMTU is sent so that
other devices can catch up with the new mtu. However, if they return
NOTIFY_BAD, then the change is reverted and error returned.

This is a really long and costy operation (sometimes). To fix this, add
NETDEV_PRECHANGEMTU notification which is called prior to any change
actually happening, and if any callee returns NOTIFY_BAD - the change is
aborted. This way we're skipping all the playing with apply/revert the mtu.

CC: "David S. Miller" <davem@davemloft.net>
CC: Jiri Pirko <jiri@resnulli.us>
CC: Eric Dumazet <edumazet@google.com>
CC: Nicolas Dichtel <nicolas.dichtel@6wind.com>
CC: Cong Wang <amwang@redhat.com>
Signed-off-by: default avatarVeaceslav Falico <vfalico@redhat.com>
Acked-by: default avatarJiri Pirko <jiri@resnulli.us>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 31cf344c

include/linux/netdevice.h

+2 −1
Original line number Diff line number Diff line
@@ -1718,7 +1718,7 @@ struct pcpu_sw_netstats { 
#define NETDEV_CHANGE	0x0004	/* Notify device state change */

#define NETDEV_REGISTER 0x0005

#define NETDEV_UNREGISTER	0x0006

#define NETDEV_CHANGEMTU	0x0007

#define NETDEV_CHANGEMTU	0x0007 /* notify after mtu change happened */

#define NETDEV_CHANGEADDR	0x0008

#define NETDEV_GOING_DOWN	0x0009

#define NETDEV_CHANGENAME	0x000A
@@ -1734,6 +1734,7 @@ struct pcpu_sw_netstats { 
#define NETDEV_JOIN		0x0014

#define NETDEV_CHANGEUPPER	0x0015

#define NETDEV_RESEND_IGMP	0x0016

#define NETDEV_PRECHANGEMTU	0x0017 /* notify before mtu change happened */



int register_netdevice_notifier(struct notifier_block *nb);

int unregister_netdevice_notifier(struct notifier_block *nb);

net/core/dev.c

+5 −0
Original line number Diff line number Diff line
@@ -5392,6 +5392,11 @@ int dev_set_mtu(struct net_device *dev, int new_mtu) 
	if (!netif_device_present(dev))

		return -ENODEV;



	err = call_netdevice_notifiers(NETDEV_PRECHANGEMTU, dev);

	err = notifier_to_errno(err);

	if (err)

		return err;



	orig_mtu = dev->mtu;

	err = __dev_set_mtu(dev, new_mtu);